To work out the ideal chicken coop size for 20 chickens, you’ll need to take several factors into consideration, but as a starting point, plan for a coop that’s at least 60 square feet.

The best size for your chicken coop will depend on the size of your chickens, their temperament, your flock management plan, and your climate.

Don’t worry, it’s easy to work everything out and in this guide I’ll cover all the space requirements you need to know about for a flock of 20 standard adult chickens and a flock of 20 bantam adult chickens.

Once you know the basics, you’ll be able to narrow down your coop purchase options or choose a set of plans to build from.

If you’re building a chicken coop out of materials you have lying around, then you can always enlarge it later if you find that it’s too small.

However, if you’re a flock owner purchasing a chicken coop or looking to build off a set of chicken coop plans, you’ll want to get the dimensions right the first time.

What’s The Ideal Chicken Coop Size For 20 Chickens?

Chickens come in different sizes, and big chickens need a bit more space than small chickens. That makes sense, doesn’t it?

Chickens also have temperaments that range from quiet and docile to active and aggressive. Their temperament is often a characteristic of their breed.

Docile chickens won’t make much of a fuss if they don’t have the biggest coop imaginable, but more aggressive breeds could quarrel and fight if they’re overcrowded. Depending on the breed you’re raising, you might want a larger coop than the recommended minimum sizes.

So chicken size and breed temperament are the first points to note down.

Next, you’ll need to decide how you’re going to manage your flock. Will you confine them to a walk-in coop or coop with attached run, or is the chicken coop only needed for overnight roosting and shelter from bad weather?

The final big consideration to think about is your climate. Are your winters harsh with snow on the ground for several months? Overnight coops work well when your flock can range on pasture, but a coop sized for overnight use would be too small for winter confinement.

Of course, a large coop isn’t the only winter option for your flock, and many flock owners put up simple, inexpensive hoop houses to give their chickens more room in the winter.

At the other end of the climate spectrum, think about your weather at the peak of summer. Where summers are hot and humid, chickens will be happier and healthier in a coop with a high ceiling and extra space, which allows more ventilation.

How Much Space Do Chickens Need Inside The Chicken Coop?

First, let’s look at the minimum space requirements for chickens using the coop for overnight shelter.

The standard allowance for small bantam breeds is 2 to 3 square feet per bird. Medium and large breeds need 3 to 4 square feet per bird.

  • For 20 bantams, the minimum overnight coop size would be 40 to 60 square feet.
  • For 20 medium or large breed chickens, the overnight coop size should be a minimum of 60 to 80 square feet.

And that’s really all the coop space you need if your chickens will be free ranging, or out in chicken tractors or runs during the day.

I built overnight coops for my chickens. During the day, they’re in chicken tractors or free ranging. But we don’t have harsh winters or large predators to worry about.

How Much Coop Space Do Confined Chickens Need?

Confined chickens need a lot more personal space. If your coop and run are going to be one unit like the walk in coop pictured below, then allow at least 8 to 10 square feet per large chicken, which gives a total coop size for 20 chickens of 160 to 200 square feet.

This image shows a wire fronted walk-in chicken coop. While this size chicken coop would provide more than enough room for overnight accommodation, it wouldn’t be large enough for 20 happy and productive chickens to live in full time.

This combined coop and run isn't an ideal chicken coop size for 20 chickens.

To maximize the space your chickens have to move around, use roosting ladders that don’t take up much floor space.

Chickens perching on a homemade roosting ladder. The roosting bars rest in notches cut into the side supports. The roosting ladder leans against the wall at an angle saving space inside the chicken coop.

For hens in a confined coop, nesting and brooding boxes should be installed along the walls, 2 – 3 feet above the ground. This arrangement ensures that all the floor space is available for the chickens.

Will Your Nesting Boxes Be Inside The Coop Or Outdoors?

Plan for 1 nesting box for every 4 to 6 hens. For 20 chickens, you’ll need 4 or 5 nesting boxes.

If you want your chickens to return to an overnight coop and lay inside, then the space for the nesting boxes should be added to the minimum space requirements.

Where a coop design is tall enough, the nesting boxes can go underneath the roosts. Just make sure you place some plastic trays over the tops of the nesting boxes to catch droppings.

If your nesting boxes will be attached to the exterior of the coop, or placed underneath a raised coop, then you won’t need to factor in nesting box space.

Don’t skimp on nesting boxes! When chickens don’t have enough nesting boxes, they’ll annoy one another by competing for space.

For example, when a hen is in the nesting box getting ready to lay an egg, the last thing she wants is another hen with an urgent need to lay her own egg pushing in.

Sometimes when hens get along really well, they’ll share a nesting box if it’s large enough, but you can’t count on that being the case.

When more than one hen is jostling for space in a nest box, any eggs already laid are more likely to get broken.

Broken eggs mean fewer eggs for you and a tasty meal for a curious chicken. Once a chicken realizes that those eggs they lay have food inside them, they’ll crack the eggs open themselves.

Egg eating is a tough habit to break, so it’s best to prevent it from taking hold.

Another problem you’ll encounter when free ranging hens don’t have enough nesting boxes is lost eggs.

Hens will wander off to search out another suitable place to lay eggs. When that happens, you’ll have fewer eggs to collect from the coop, and even worse, a big pile of decaying eggs will build up under a bush or in a big scrubby patch of grass.

Does Your Coop Need Broody Boxes?

If you plan to allow your hens to sit on eggs if/when they go broody, then they need a place in the coop for the 3 week setting period and you should factor that space into your coop design.

Broody boxes, like nesting boxes, can be raised up so they don’t take up any additional floor space if your coop design is tall enough.

Chicken Coop Size Guidelines For 16 – 20 Medium/Large Chickens

Medium and large breeds are known as standards. Medium size breeds are light standards, larger breeds are heavy standards.

Overnight Coop

Allow 3 to 4 square feet per chicken for overnight roosting in the coop. For 20 chickens the minimum coop size you need is 60 to 80 square feet.

Combined Coop & Chicken Run

Allow at least 8 to 10 square feet per chicken for confined hens. For 20 chickens the minimum space you need in the coop and chicken run is 160 to 200 square feet.

Roosting Bars

You’ll need approximately 30 feet of roosting bars for 20 chickens depending on how many chickens you put on each roost.

Each chicken should have 10 – 12 inches on the roosting bar, and the roosting bars should have 18 inches between the end roost spaces and the coop walls.

For example if you put 5 birds on each roost bar as shown below, the total length of the bar would be 96 inches or 8 feet. You would need 4 roost bars for a total of 32 feet.

Illustration showing roosting bar space for chickens.

The reason for the extra space at the ends of roost bars is so that chickens aren’t crammed up against the walls of the coop in winter. It’s much colder right next to the coop walls and birds can get too chilled.

Nesting Boxes

For 20 chickens, you’ll need 4 or 5 nesting boxes. For large hens, nesting boxes need to be 12 – 14 inches wide and 18 inches high.

Medium/large chicken breeds include:

  • Australorp
  • Brahma
  • Buff Orpington
  • Cochin
  • Cornish
  • Delaware
  • Dorking
  • Favorelle
  • Jersey Giant
  • Old English Game
  • Maran
  • New Hampshire
  • Plymouth Rock
  • Rhode Island Red
  • Sussex
  • Wyandotte

Chicken Coop Size Guidelines For 20 Bantam Chickens

Bantam chickens vary in size depending on the breed they’re derived from. A bantam Orpington, for example, weighs around 3 pounds, while a bantam Leghorn only weighs 1.5 pounds.

If you’re raising bantam leghorns for eggs, your coop won’t need to be as large as a coop for a larger bantam breed.

Overnight Coop

Allow 2 to 3 square feet per chicken for overnight roosting in the coop. For 20 chickens the minimum coop size you need is 40 to 60 square feet.

Combined Coop & Chicken Run

Allow at least 6 square feet per chicken for confined hens. The minimum space you need in the coop and chicken run is 120 square feet.

Roosting Bars

You’ll need roughly 16 to 24 feet of roosting bars for 20 bantams depending on their size.

Each chicken will need 6 – 8 inches on the roosting bar and the roosting bars should have 18 inches between the end roost spaces and the coop walls.

For example you could put 7 larger bantams on an 8 foot roost bar. For 20 chickens you’d need 3 roost bars for a total of 24 feet.

Illustration showing roosting bar spacing for bantam chickens.

Nesting Boxes

For 20 bantam chickens, you’ll need 4 or 5 nesting boxes. For bantam hens, nesting boxes need to be 10 inches wide and 12 inches high.

The specifications above are only minimum sizes and chickens appreciate as much space as you can give them.

Lack Of Coop Space Can Cause Behavioral Problems In Your Flock

Chickens love space. They’ll tolerate confinement and some nervous types seem to prefer the safety of a confined run rather than open pasture, but if chickens are overcrowded, they’ll squabble and fight for space.

Instead of having a stable pecking order where every chicken feels secure, you’ll have more aggressive behavior, which could lead to injuries.

Aggressive behavior also causes stress in the flock, which isn’t good for their health or for productive egg laying.

Undersized Coops Are Prone To Ventilation Problems

Chicken coops need lots of air flow. A well-ventilated coop prevents respiratory ailments and some other nasty conditions.

Chickens poop a lot even when they’re only using the coop at night. The nitrogen in their droppings breaks down into ammonia and when ammonia builds up, it can cause infectious bronchitis and contact sores and ulcers on legs and feet.

Overcrowding Helps Parasites Spread Through your Flock

When chickens are crowding together for long periods, it’s much easier for mites and lice to spread through your flock.

If you get an infestation of mites in your coop, your chickens will be reluctant to use the coop. You’ll find it harder to put the chickens away for the night, and hens won’t want to use the nest boxes.

When hens have parasites, they can stop laying, the quality of the eggs deteriorates, and the overall health of the flock suffers. Severe infestations of some types of mite, like the Red Spider Mite, can be fatal in poultry.

Lack Of Coop Space Could Result In Dirty Eggs

Without enough roosting space, hens sleep wherever they can and that includes in your nesting boxes.

When a hen sleeps in a nesting box, she’ll leave a lot of chicken poop behind, and that poop will get on your eggs.

Future Proof Your Coop

If you plan on expanding your flock in the future or raising chicks to replace layers as they age, it makes more sense to go with a larger coop from the start rather than try to enlarge the coop later (unless you’re a handy type).

With extra space in the coop, you can section an area off to use as a brooder. Integrating chickens of different ages takes time and until they can all roost together, the young chickens need their own space.

Why Building A Chicken Coop From Plans Could Be Better Than Buying One

This is my subjective opinion, and what’s right for me may not work for you, but building a chicken coop isn’t hard at all, and you’ll save a lot of money if you buy or scrounge up some materials and get busy.

Ready-made chicken coops are so expensive for what they are, and if you haven’t price shopped yet, get ready for sticker shock.

Years ago, I learned to frame and build houses by watching videos of the old PBS show Hometime with Dean Johnson.

You might think I’d get my feet wet by building a shed or a chicken coop, but in fact, I project managed and helped with the construction of my first house build (7000 square feet). Then, with my husband, I built a 3000 square foot house. The only work we didn’t do ourselves was running the backhoe for the foundations.

The reason I mention this is to stress how easy it is to build something as basic as a chicken coop.

Old Sheds Make Practical & Affordable Chicken Coops

You could score a free chicken coop by looking on your local Facebook Market place for sheds that people want to get rid of. An 8 by 10 foot backyard shed would be perfect for an overnight coop or for a coop with an attached run.

Look at this shed coop on the Whitepepper Farms YouTube channel for inspiration.

Keep costs front and center when you’re working out your chicken coop budget.

How many eggs will your chickens need to lay before you break even on the initial setup cost?

A chicken coop is definitely an investment, and as long as you maintain your coop it will last for many years to come. But like any investment, the sooner you see a profit, the better.

Thanks for reading: What’s The Ideal Chicken Coop Size For 20 Chickens?

bio pic

Kate Prince

Hey there! I’m a small scale homesteader sharing what I know about the off-grid life. I grow fruits and vegetables, raise chickens and goats, and produce my own power, heat, and clean water.   Feel free to send me a message.